The connective tissues of the periodontium are well vascularized allowing invading microorganisms which as the periodontal pathogen P. gingivalis to readily enter the blood stream. Infection with P. gingivalis and the biological consequences for increased risk for cardiovascular disease have recently received considerable attention. We have recently established that P. gingivalis is capable of invading aortic, heart, and vein endothelial cells and that fimbriae are required for adherence to and invasion of endothelial cells. Preliminary studies indicate that adherence of P. gingivalis to the endothelial cell induces signal transduction events in the endothelial cell and that cytoskeletal rearrangements are required for internalization of attached bacteria. To examine the specificity of the interactions between P. gingivalis fimbriae and the endothelial cell surface, and to assess the cellular mechanisms concurrent with P. gingivalis invasion of endothelial cells, the following specific aims are proposed. Aim 1. To define the molecular interactions of P. gingivalis fimbriae with the human endothelial cell receptor. We will define the binding domain of P. gingivalis fimbriae for human endothelial cells using reagents to defined regions of fimbriae. We will also identify the high affinity endothelial cell receptor to which P. gingivalis fimbriae bind. Aim 2. To define the cellular mechanisms involved in P. gingivalis invasion of endothelial cells. We will determine if P. gingivalis is internalized by receptor mediated endocytosis and begin to define the signal transduction events during P. gingivalis invasion of endothelial cells. These will be examined following invasion of endothelial cells by P. gingivalis 381 and a fimA deletion mutant and will be characterized by confocal microscopy. Regulation of specific endothelial adhesion molecules (E-selectin, P-selectin, VCAM-1, and ICAM-1) and induction of cytokines (IL-1, IL-8, MCP-1, and TNF-alpha) will be assessed following invasion of endothelial cells by P. gingivalis 381 and the fimA deletion mutant. The ability to multiply in and to activate endothelial cells might be one of the pathogenic mechanisms exerted by P. gingivalis that may explain the observed association between this organism and coronary heart disease.